Impairments in social behavior are a hallmark of moderate-to-severe traumatic brain injury (TBI) in adults. Social behavior problems are stable over time, and are a major source of stress and burden for caregivers. These problems can lead to loss of employment and social isolation, which in turn are associated with a high risk of depression, suicidal ideation, and poor quality of life among adults with TBI. Thus, social problems are a common, chronic, and costly problem for individuals with TBI and their caregivers. While TBI can result in a range of cognitive and behavioral disorders, the most common complaint, and perhaps the greatest obstacle to community re-integration and employment, is that persons with TBI have odd social behaviors, such as making inappropriate or irrelevant comments, monopolizing conversations, and generally appearing to be insensitive to the social needs of others. These are social communication problems. Social communication problems have been well documented in the TBI research and clinical literature. To date, however, there is little evidence that treatment of these problems generalizes beyond the therapy room to everyday social interactions. Traditional treatments focus on re-teaching appropriate behaviors (e.g., training eye contact or turn-taking). The limited success of these treatment methods may be the result of failing to consider the underlying causes of behavior problems. Specifically, there is growing evidence that the cause of impaired performance may be failure to read social cues, i.e., impaired social perception. Social perception problems after TBI may range from failure to read basic nonverbal cues such as gaze direction, to errors perceiving complex social cues such as sarcasm. An understanding of social perception problems in adults with TBI is critical for treatment planning: if the patient cannot perceive socil cues, he or she will not know when to execute learned behaviors outside of the structured therapy environment. To develop effective treatments, it is necessary to understand social perception problems in adults with TBI and determine how these problems relate to specific communication behaviors. This is the aim of the proposed research. The studies also will examine sex-related differences in social perception, as this potential contributor to differences in communication outcome has not been considered in previous research. The findings will lead directly to improved intervention approaches for adults with TBI, and will advance theoretical and clinical knowledge about human social communication in the context of everyday life.